This invention relates to halogeno-4-methylpyrazoles useful as intermediates for pharmaceuticals and agricultural chemicals, etc. and processes for producing the same, more particularly to 5-halogeno-1-substituted-4-methylpyrazoles and 3,5-dihalogeno-1-substituted-4-methylpyrazoles and processes for producing these.
Chemical Abstract vol. 71, 112859i discloses that no halogeno-methylpyrazole is formed, but a trimer is formed by bromination of 4-methylpyrazole.
Journal of Agricultural Food Chemistry (J. Agrc. Food. Chem.), vol. 25, No. 4, p. 884 (1977) discloses a process for preparing 4-methyl-3,5-dibromopyrazole which comprises permitting butyl lithium to act on 3,4,5-tribromopyrazole, followed by substitution with methyl iodide.
However, this process cannot be said to be an industrial production process, because synthesis of 3,4,5-tribromopyrazole is complicated, and moreover the synthesis steps are lengthy, and yet expensive butyl lithium is used.
Chemical Abstract Vol. 66, 94950x discloses a process for preparing 3-bromo-1,4-dimethylpyrazole which comprises brominating 1,4-dimethyl-5-hydroxycarbonylpyrazole, followed by decarboxylation.
However, this process cannot be said to be an industrial production process, because 1,4-dimethyl-5-carboxypyrazole is expensive, and the synthesis steps are complicated.